View source for AC adapter

[[Category:Done 2015-07-01]] 
[[File:AC adapter.jpg|framed|Figure 1. An AC adapter used for charging a laptop battery.]]
<onlyinclude>'''AC adapters''' convert a higher-[[voltage]] [[alternating current]] to a lower-voltage [[direct current]] for use with devices that require constant current and voltage.</onlyinclude> Direct current is also required to recharge batteries, making AC adapters essential for electronic devices like laptops (see figure 1) and cell phones.<ref>''What's the difference between AC and DC?'' [Online]. Available: http://engineering.mit.edu/ask/what%E2%80%99s-difference-between-ac-and-dc</ref> Older AC adapters waste quite a bit of [[electricity]] in the form of [[standby power]], but recent regulations and subsequent innovations have reduced the amount of electricity wasted considerably.

==How it works==
A simple AC adapter consists of a [[transformer]], a rectifier, and an [[electronic filter]]. The transformer initially converts a relatively high-[[voltage]] [[alternating current]] that is supplied by an [[electrical outlet]] to a lower voltage suitable for the device being powered.<ref>''Insight-How Adapter Works'' [Online]. Available: http://www.engineersgarage.com/insight/how-adaptor-works</ref><ref>''Inside a Power-Cube Transformer'' [Online]. Available: http://science.howstuffworks.com/environmental/energy/inside-transformer1.htm</ref> A rectifier then converts [[alternating current]] into [[direct current]]. There are two separate types of rectifiers: the half-wave rectifier and the full-wave rectifier.

===Half-wave rectifier===
The half-wave rectifier effectively blocks current flow in one direction through the use of a [[diode]] (see figure 2). This creates a pulsating direct current. Due to half of the current being blocked, much of the supplied energy is lost, and the mean voltage of half-wave rectified power is lower than that of full-wave rectified power.
[[File:Half-wave rectifier.png|framed|center|Figure 2. A half-wave rectifier.<ref>''File:Half-wave rectifier'' [Online]. Available: http://commons.wikimedia.org/wiki/File:Halfwave.rectifier.en.svg</ref> The arrow-shaped symbol at the top of the circuit is a diode that only allows [[electron]] flow from right to left across the diode. The graph on the left is the input voltage and the graph on the right is the output voltage.]]

===Full-wave rectifier===
There are several types of full-wave rectifiers. Rather than blocking the [[current]] in one direction, these rectifiers flip its direction so that a constant pulsing [[direct current]] is the output. A common type of full-wave rectifier is the full-wave bridge rectifier<ref>''Rectifier circuits'' [Online]. Available:http://www.allaboutcircuits.com/vol_3/chpt_3/4.html</ref> (See Figure 3). 
[[File:Full-wave bridge rectifier.png|framed|center|Figure 3. A full-wave bridge rectifier.<ref>''File:Gratz.rectifier.en.svg'' [Online]. Available: http://commons.wikimedia.org/wiki/File:Gratz.rectifier.en.svg</ref> The graph on the left is the input voltage and the graph on the right is the output voltage.]]

For more information about rectifiers, visit [http://www.electronics-tutorials.ws/diode/diode_6.html ''ElectronsTutorials''] or [http://www.allaboutcircuits.com/vol_3/chpt_3/4.html ''All About Circuits''].

===Smoothing===
[[File:Smoothing Capacitor.png|framed|right|Figure 4. The output voltage (green) of a half-wave rectifier and smoothing capacitor from the input AC voltage (yellow). Note the ripples in the output voltage.]]
As seen in Figures 2 and 3, the output voltage of the two rectifiers still varies greatly. However, a constant voltage is required for most devices that operate on [[direct current]]. A smoothing circuit or [[capacitor]] is used to achieve this. At its simplest, a circuit component known as a reservoir capacitor or smoothing capacitor is placed at the output of the rectifier. Essentially it releases stored energy when no voltage is being output from the rectifier.<ref>''What's a smoothing capacitor?'' [Online]. Available: http://www.learningaboutelectronics.com/Articles/What-is-a-smoothing-capacitor</ref> This creates a fairly steady voltage. However, some ripples from the AC voltage remain (See Figure 4).

==References==
<references/>
[[Category:Uploaded]]